1. Field
The present disclosure relates generally to communication systems, and more particularly, to an apparatus and method for improving demodulation reliability of an uplink high-speed dedicated physical control channel (HS-DPCCH).
2. Background
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
In heterogeneous networks, for example, HSPA networks, a severe imbalance may exist in downlink and uplink path loss between a user equipment (UE) and cells belonging to an active set of the UE. The imbalance may be caused by differences in transmit powers of a macro cell and a small cell which may be in the UE's active set.
As serving cell selection in HSPA is based on downlink (DL) radio conditions, the DL and UL boundaries could be different. In other words, the point at which DL Ecp/Io from the serving cell and a non-serving cell match may be different from the point at which the UL effective path loss match for the serving cell and the non-serving cell. Additionally, at the points where the DL path loss from the serving cell is better than the non-serving cell, the non-serving cell could have a much better uplink path loss. Thus, due to existing power control procedures in CDMA, the transmit power of the UE may be power controlled down to a point where the uplink (UL) high speed dedicated physical control channel (HS-DPCCH) may not be reliably demodulated by the serving cell.
As the UE transmit power is effectively power controlled by a non-serving cell, the uplink SINR experienced at the serving cell may fluctuate a lot, and hence even if the HS-DPCCH power were to be boosted, it may not be reliably demodulated at the serving cell.
Thus, there is a desire for a method and apparatus for improving demodulation reliability of an uplink (UL) HS-DPCCH at a base station.